I suggest putting a police car in every school parking lot.

[WhaTHellsgoingonhere]

2. I've seen this in Chicago (sort of)

I don't know the logistics, how often they do this, how long they stay, or even which schools, but there's a high school near me that gets a lot of police attention during the day. I've seen 1 or 2 squad cars parked in front. I've also seen squad cars just drive by slowly. But this isn't Columbine. This is a city school and the building is very close to the street.

The schools definitely don't employ a cop or security guard full-time. Patroling the school just appears to be part of the police's beat.